Instantaneous high-capacity heater for a gaseous medium



Nov. 10, 1964 FLYNN 4 INSTANTANEQUS HIGH-CAPACITY HEATER FOR A GASEOUS MEDIUM Filed Jan. 16, 1963 ,I J M United States Patent 3,156,454 INSTANTANEOUS HIGH-CAPACITY HEATER FOR A GASEOUS MEDIUM .l'ohn H. Flynn, 234 Elk Ave., New Rochelle, N.Y. Filed Jan. 16, 1963, Ser. N 252,276 3 Ciaims. (Cl. 26319) This application is a continuation in part of my prior application, Serial No. 100,483, filed March 30, 1961, now abandoned, which was a continuation of my prior application, Serial No. 826,832, filed July 13, 1959, now abandoned.

This invention relates to air heaters in general, and to instantaneous high-capacity air heaters in particular.

It is the primary aim and object of the present invention to provide an air heater of a type which not only produces hot air instantaneously and also continuously, but has also a large output capacity for its size.

It is another object of the present invention to provide an air heater of this type in which the air passing therethrough is compelled into optimum exposure to the heat from a flame therein, by providing in the heater successive first and second zones in which the passing air closely envelops the flame and is in intimate comingling relation with the flames products of combustion, respectively, with the air passing through the heater having therein a lowest possible displacement rate under least turbulent conditions within this first or flame zone for optimum heat transfer from the flame to the enveloping air so that, with the subsequent pass of the thus preheated air through the second zone in intimate heatexchange relation with the flames products of combustion, the ultimate in heat transfer to the air on its pass through these two zones is substantially reached.

It is a further object of the present invention to provide an air heater of this type in which the aforementioned lowest possible displacement rate of the passing air under least turbulent conditions in the first zone thereof is achieved, by providing in the heater a longitudinal chamber with a lateral air inlet of which a forward section remote from the air inlet and continuous with the second zone forms the first zone and is of a cross-sectional area which in the first place is larger than that of the second zone, and in the second place is as large as possible while still being sufficiently restricted to keep the passing air in the required close heating proximity to the flame therein, and by making provision for largely suppressing turbulence of the air in this chamber ensuing from the forced air admitted thereinto through the inlet.

Another object of the present invention is to provide an air heater of this type in which the aforementioned provision for suppressing air turbulence in the longitudinal chamber thereof is in the simple form of an air dome in tihs chamber. To this end, the air dome is simply formed by a rear section of the chamber which is closed at the rear end of the latter and open to the rest of the chamber, whereby this chamber'is throughout its longitudinal extent advantageously of substantially the same restricted cross-sectional area within which air passing through the forward section of this chamber is kept in the aforementioned close heating proximity to the flame therein. Furthermore, the air inlet is arranged to direct the forced air into the chamber transversely thereof and also sufliciently behind the forward section thereof so that the flame therein is out of the direct path of this forced air and, even more important for effective air turbulence suppression, the air inlet is spaced from the closed rear end of the chamber sufliciently so that the part of the chamber therebetween, being the air dome defining or depth to function effectively in suppressing the high 3,155,454 Patented Nov. 10, 1964 turbulence of the nearby air and compelling substantially uniform and non-turbulent air flow through the forward section of the chamber past the flame therein and into the aforementioned succeeding second zone of the heater.

Other objects and advantages will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for ilustrative purposes:

FIG. 1 is a view of an air heater embodying the present invention; and

FIG. 2 is a section through this heater substantially as taken on the line 22 of FIG. 1.

Referring to the drawings, the reference numeral 10 designates an air heater having a longitudinal body or casing 12 with an output or discharge end 14. The casing 12 provides a substantially cylindrical chamber 16 having air admission means in the form of a preferably circular port or inlet 18 which for reasons explained hereinafter is spaced considerably from the closed end of the casing opposite its discharge end 14. Extending into the casing chamber 16, in this instance axially thereof, is a burner tube 24) with an end in the form of a nozzle 21 with a flame opening of a given mean cross-sectional dhnension from which emanates a flame F that extends axially of the chamber 16 between the air inlet 18 and the discharge end 14 of the casing and points toward this discharge end. Received in the casing chamber 16 is a ceramic body orv liner 22 which is provided with a central throughpassage 24 having a substantially cylindrical wall 26.

.The discharge end 14 of the casing 12, which is arranged next to the outlet end 28 of the ceramic liner 22, is in this instance formed as a manifold 30 having hot air outlets 32 in an end plate 34. V

The burner tube 20 is part of a known blast burner unit 36 having a burner body 38 from which the tube 20 extends, and a fuel-air mixer 40 to which are conducted combustion air under pressure and fuel, presently gas, through conduits 42 and 44 respectively. The gas conduit 44 is in communication with any suitable fuel gas source (not shown) and has interposed regulator and shut-ofi valves 46 and 48. The mixer 40 is of known Venturi type in which the admitted combustion air under pressure draws gas from theconduit 44 at a proportion dependent on a manual gas-ratio setting of the shut-off valve 48 and on automatic setting of the regulator valve 46 in a manner explained hereinafter. The gas-air mixture passes from the mixer 49 through the burner body 38 and tube 20 and through a ported insert 50 in the burner nozzle 21 where the mixture is ignited, in this instance by momentary spark ignition from an electrode 52, with the ensuing flame F being sustained by the constantly fed gas-air mixture. FIG. 2 also shows a flame rod 54 in contact with the flame F. This flame rod 54 is part of a conventional flame-rectification type flame failure safety control which forms no part of the present invention, and, hence, requires no further explanation. The heater casing 12 is preferably also provided on one side with a sight glass 56 through which to View the flame F, and on its opposite side with an explosion plug 58 which will be blown out if the aforementioned flame failure safety control should perchance fail and an accumulation of gas in the heater casing be ignited belatedly.

The air to-be-heated is drawn from the atmosphere into a power-driven blower 60 which delivers the air at a certain pressure into a conduit 62 that is in communication with the inlet 18 in the heater casing 12. A manually operable butterfly valve 64 in the conduit 62 serves for regulation of the volumetric flow rate of the air to the heater and, hence, of the hot-air output rate of the latter.

The flame F emanating from the burner nozzle 21 is a high velocity flame of high heat intensity. Since relatively high output capacity of the present heater for its size is one of the objectives, the air in the heater casing 12 may be under considerable pressure, requiring even greater pressure of the gas-air mixture in the burner tube to sustain the flame F and keep it sharp and stable in the axial direction of the heater casing 12. The flame F, which is subject to regulation as described herein after, will for etficient performance of the heater reach substantially to, and may even reach into, the passage 24 in the ceramic liner 22 so that this liner passage 24 will be in the most immediate path of the flames products of combustion, and the flame will at least at its tip be also in effective heat-exchange relation with the inner wall 26 of the liner at least at the inlet end 66 of its throughpassage 24. Also, the inner wall 26 of the ceramic liner 22 at the inlet end 66 of the passage 24 is flared outwardly at 70 into relatively close proximity to the wall 72 of the chamber 16 in the heater casing 12.

For most economic operation of the present heater, the hot-air output of the same may also he regulated in accordance with varying demands for volume. achieved in the present instance quite simply by setting the described butterfly valve 64 in the cold-air conduit 62, as will be readily understood.

The velocity and heat intensity of the flame F for a desired temperature of the issuing hot air and for complete combustion of the gas-air mixture at the flame F may be regulated by adjusting the compression of the combustion air admitted into the mixer of the burner unit 36, and by setting the manual valve 48 to a appropriate gas-ratio position. In order further to regulate the gas-air mixture for its complete combustion at the flame F on varying the output rate of the eater, the regulator valve 46 is of a commercial type having a chamber 76 divided into compartments 78 and 80 by a diaphragm 82. The valve 46 is responsive to air pressure in compartment 80, while compartment 78 is subjected to the pressure of the air passing through the heater by being connected therewith, presently with the casing chamber 16, through a conduit 84. Thus, on increasing or decreasing the output rate of the heater and, hence, the pressure of the air flowing therethrough, the diaphragm valve 46 will respond by passing varying amounts of gas to maintain complete combustion of the gas-air mixture at the flame.

The discharge end 14 of the heater casing 12 and, hence, the manifold 30 thereat presently extend laterally of the casing (FIG. 1) to afford a substantial area for a relatively large number of outlet ports 32 for simultaneously subjecting a correspondingly large work area to hot air jets from these ports.

In operation of the heater, the air to-be-heated will enter the casing chamber 16 through the inlet 18 and then advance axially in this chamber in enveloping relation with the flame F therein and thus become preheated. The air then passes into and through the passage 24 in the ceramic liner 22 in which it is further heated to its ultimate high temperature by the flames products of combustion, with the hot air then passing into the manifold 30 and out through the ports 32 in the form of hot air jets.

The present heater is designed to compel air passing therethrough into optimum exposure to the heat from the flame F. To this end, the air is heated in two successive stages in the first stage of which the air envelops the flame and is thus heated directly by the flame, and in the second stage of which it is brought into intimate commingling relation with the flames products of combustion and thereby heated to its ultimate high temperature. The first-stage heating of the air takes place in a forward or flame zone of the non-lined part of the casing chamber 16 between the burner nozzle 21 and the This is liner 22, while the second-stage heating of the air takes place in another zone which is formed by the liner passage 24. To achieve optimum heat transfer from the flame to the passing air in the flame zone, the air must have optimum dwell in this zone and must also be substantially non-turbulent in this zone. Optimum dwell of the air passing through the flame zone is achieved by keeping the cross-sectional area of the exemplary cylindrical casing chamber 16 at its maximum at which all of the passing air in the flame zone is still kept in sufficiently close proximity to the flame therein to he preheated by the so no to the extent necessary in order to reach on its succeeding pass through the liner passage the ultimate high temperature required for a given maximum output rate of the heater.

With the heater being adapted for high output capacity for its size, the amount of air forced by the blower 60 at any instant through the inlet 18 into the casing chamber 16 is correspondingly large, with the result that the air thus forced from the inlet into the confronting part of the chamber 16 sets up air turbulence therein. In accordance with an important aspect of the present invention, this air turbulence in the chamber 16 is largely suppressed by an air dome feature in this chamber, so that the air may pass to and through the flame zone in this chamber in the required substantially non-turbulent condition. The air dome is formed conveniently and advantageously by the rear section or part or" the chamber 16 which extends from the closed rear end of the latter to the inlet 18. With the casing chamber 16 being preferably cylindrical, the air dome is of the same cross-sectional area as the hereinbefore qualified cross-sectional area of the flame zone of the chamber, with this air dome being also of adequate depth, i.e., extent axially of the chamber 16, to perform its designated function of largely suppressing air turbulence in the chamber and compelling substantially non-turbulent air flow to and through the flame zone. Further, in order that the air dome may act most effectively not only to suppress air turbulence but also to compel substantially uniform air flow through the flame zone throughout its cross-section around the flame therein for optimum heat-exchange of the passing air with the latter, care is taken that air turbulence in the chamber 16 just ahead of the air dome occurs throughout the cross-section of the chamber thereat so that turbulent air will confront the air dome throughout its cross-sectional area. This is achieved by making the inlet 18 of a cross-sectional area sufiiciently large so that the amount of forced air passing therethrough per time unit Will set up the desired total air turbulence in the confronting part of the chamber cross-sectionally throughout. In order to achieve substantially uniform and non-turbulent air flow through the flame zone in the casing chamber 16 by the action of the described air dome, it is, of course, imperative that the burner nozzle 21 in the chamber is spaced forwardly from the inlet 18 sufiiciently so that the flame F is not only out of the direct path of the air forced into the chamber through the inlet, but is also out of effective reach of the turbulent air being acted upon by the air dome in compelling it into substantially uniform and non-turbulent flow in the chamber.

The air heater shown in FIGS. 1 and 2 is in all respects exactly like an actual heater of larger size which proved to be highly efficient in its performance to heat air to varying high temperatures at relatively widely varying output rates, with the air dome functioning entirely satisfactorily in largely suppressing air turbulence in the chamber and compelling substantially uniform and nonturbulent air flow to and through the flame zone at each performance of the heater. The specific heater shown in the drawings thus serves as a good example of a heater of the present invention which by the illustrated arrangement and coordination of the non-lined part of its chamber 16, its inlet 18 and its burner nozzle 21 in the chamber, fully secures the described air dome effect on the air in the chamber. In a broader sense, this specific heater demonstrates some basic dimensional relations of the structure involved in achieving the designated function of the air dome which will serve as a general guide in securing the same beneficial air dome effect in heaters which in their specific dimensional relations may widely differ from those of the specific heater shown. Thus, the part of the chamber 16 confronting the air inlet 18 and the continuing part of the chamber extending to the closed rear end thereof have a combined axial length which is larger than that of the flame zone, and the inlet 18, being of exemplary circular outline, has a cross-sectional area which, in comparison to that of the chamber 16, is sutficiently large so that air forced therethrough at even fairly moderate pressure will strike with sufficient force into the confronting part of the chamber 16 to set up air turbulence therein cross-sectionally throughout, as required. Also generally applicable for the design of air heaters with the beneficial air dome effect is the arrangement of the non-lined part of the casing chamber 16 such that the combined length of the chamber part confronting the inlet 18 and the adjacent chamber part continuing to the closed end of the chamber is larger than the crosssectional dimension of the chamber. Also still generally applicable for the design of air heaters with the beneficial air dome effect is the arrangement of the non-lined part of the casing chamber 16 such that its overall length is several times larger than its cross-sectional dimension, and the air dome part of this chamber is only several times shorter than the overall length of the non-lined part of the chamber. It thus becomes a simple matter to design an air heater of this type of most any size and for most any application, and embodying the air dome feature, by following any one or more of the aforementioned basic dimensional relations.

Further affecting the performance of the specific heater shown in reaching the desired ultimate high temperature of the output air at a given high air output rate are the size of the flame F in length and width and its extent in the flame zone of the passage 16, and the cross-sectional area and length of the liner passage 24. The size of the flame F is largely determined by the mean crosssectional width, i.e., diameter, of the preferably cylindrical flame opening in the burner nozzle 21, and the pressure of the combustible gas-air mixture that feeds and sustains the flame. In this specific example, the mean cross-sectional dimension of the flame opening is only several times smaller than the cross-sectional dimension of the chamber 16 and, further, the mean crosssectional dimension, i.e., diameter, of the exemplary circular air inlet 18 is several times larger than the mean cross-sectional dimension of the flame opening. Further, the pressure of the combustible air-gas mixture feeding the flame is such that the same preferably extends substantially the full length of the flame zone which in this specific example is several times longer than the mean cross-sectional dimension of the flame opening in the burner nozzle 21. These specific comparative dimensions of the flame and flame zone are applicable where relatively high air temperatures at high output rates are required. Insofar as the cross-sectional area of the liner passage is concerned, the same may readily be selected to achieve therein intimate commingling of the flames products of combustion with the pressing air, while the length of the liner passage may readily be determined so that on the brief pass of the air therethrough the latter will absorb the intense heat of the products of combustion to the optimum extent. The cross-sectional area of the liner passage is in this specific example constricted to the extent shown in the drawings, and the length of the liner passage is less than that of the non lined part of the chamber 16 between its closed rear end and the liner.

It follows from the preceding that an efiicient air heater of the featured air dome type may be designed in many different sizes and for many different applications and ultimate hot air temperatures and air output rates, by following one or more of the explained basic dimensional relations in the arrangement and coordination of the non-lined part of the casing chamber, the air inlet and the location of the burner nozzle in the chamber, with the more specific dimensional relations given respecting the fiame and liner in the chamber of the heater shown affording some guidance in arriving at different dimensional relations thereof best suited for different ultimate air temperatures at the same or difierentoutput rates. Of course, the heat intensity of the flame will in each instance be one of the important factors in determining the ultimate high temperature of the heated air.

It is also evident that 'a heater of this type may be operated to meet relatively widely varying performance requirements. Thus, the exemplary heater shown may be operated to deliver air at a lower high temperature but higher output rate by simply increasing the input rate of air into the heater without any other change. Conversely, the same heater may be operated to deliver air at increased high temperature but reducedoutput rate by simply reducing the input rate of air into the heater without 'any other change. Also, the same heater may be operated to deliver air at decreased or increased high temperature at the same output rate by corresponding regulation of the heat intensity of the flame without any other change. Of course, these and other changes in the performance of the heater are kept within limits at which the heater functions efiiciently in all respects, including the air dome effect.

While the liner 22 is preferably and advantageously of ceramic type and thus not only aids in heating the passing air by radiating into the same a good deal of the heat absorbed thereby, but is also instrumental in keeping heat loss to the outside of the heater casing at a minimum, the liner may be a mere cross-sectional constriction in the burner casing without changing any of the inventive aspects of the heater. Finally, insofar as the featured air dome in the chamber is concerned, its full effect and benefit is obtained even if the part of the burner ahead of the flame is arranged differently than in the form of a ceramic liner or cross-sectional constriction of the chamber.

Given only by way of example and by no means by way of limitation, the following is an account of an actual specific performance of a certain heater which points at the very high efliciency of heaters of the present air dome type. This certain heater, referred to for the sake of convenience as a test heater, was in all its dimensional relations quite similar to the heater shown. The actual dimensions of this test heater were as follows. The nonlined part of the casing chamber was cylindrical, of 3 inch diameter and approximately 9 inches in length, and the ceramic liner had a through-passage coaxial with the casing chamber of 6 /8" length and 1%" diameter beyond its flared end. The air inlet to the casing chamber was circular in cross-section and of the same diameter as the chamber, namely 3", and this inlet was at its center spaced from the closed end of the casing chamber a distance of approximately 3". The burner tube, which extended through the closed chamber end into the chamber axially thereof, was 1" in outer diameter and had a nozzle with a flame opening of slightly less than 1, with the end of the nozzle being spaced from the liner a distance of slightly over 2 /2". The air dome part or section of the casing chamber thus was of a minimum axial extent or depth of approximately 1 /2, while the flame end of the burner nozzle, being between the air inlet and liner, was spaced from the air inlet a distance of approximately 1 /2. The flame from the burner nozzle reached substantially to the liner, and the flame was regulated to generate 23,000 B.t.u. per hour. Air from a blower was forced through the inlet into the casing chamber at a rate of cubic feet per minute, with the static pressure in the flame zone being determined at 2.40 water column. The velocity of the air in the casing chamber near the tip of the flame was determined at 1837 feet per minute, while the velocity of the air in the liner passage was measured at 7438 feet per minute. The air had a temperature of 70 F. when entering the heater and had a temperature of 600 F. when leaving the ceramic liner. Thus, in continuous operation of the heater 90 cubic feet per minute were heated from 70 F. to 600 F. with a mere 383 B.t.u. per minute.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

What is claimed is: I

1. An air heater, comprising a casing providing a substantially cylindrical chamber and means providing opposite closed and open chamber ends and a lateral air inlet to said chamber between said ends; a burner tube extending through said closed chamber end into said chamber axially thereof and having a burner end with a flame opening of a given mean cross-sectional dimensiond from which to project an axial flame toward said open chamber end; means for forcing air through said inlet into the confronting part of said chamber transversely thereof; and a tubular ceramic liner in said chamber between said open end thereof and said burner end and providing a through-passage substantially coaxial with said chamber, said chamber being of a cross-sectional dimension several times larger than said dimension d and being between said closed chamber end and liner of a length several times larger than said cross-sectional chamber dimension, said burner end being located between said air inlet and liner and axially spaced from said liner a distance several times larger than said dimension d, and said air inlet being of a mean cross-sectional dimension several times larger than said dimension d to compel the forced air to set up air turbulence in said confronting chamber part crosssectionally throughout, with said air inlet being so spaced from said closed chamber end that the end part of said chamber therebetween is only several times shorter than the length of said chamber between said closed end thereof and said liner, whereby said chamber end part will serve as an air dome in largely suppressing air turbulence in said chamber and compelling substantially uniform and non-turbulent air flow past a flame from said burner end and into said liner passage.

2. An air heater as set forth in claim 1, in which said air inlet is substantially circular and of larger cross-sectional dimension than said liner passage.

3. An air heater as set forth in claim 1, in which the length of said chamber between said closed end thereof and said liner is larger than the length of said liner.

References Cited in the file of this patent UNITED STATES PATENTS 2,110,209 Engels Mar. 8, 1938 FOREIGN PATENTS 535,482 Great Britain Apr. 10, 1941 556,169 Great Britain Sept. 22, 1943 

1. AN AIR HEATER, COMPRISING A CASING PROVIDING A SUBSTANTIALLY CYLINDRICAL CHAMBER AND MEANS PROVIDING OPPOSITE CLOSED AND OPEN CHAMBER ENDS AND A LATERAL AIR INLET TO SAID CHAMBER BETWEEN SAID ENDS; A BURNER TUBE EXTENDING THROUGH SAID CLOSED CHAMBER END INTO SAID CHAMBER AXIALLY THEREOF AND HAVING A BURNER END WITH A FLAME OPENING OF A GIVEN MEAN CROSS-SECTIONAL DIMENSION D FROM WHICH TO PROJECT AN AXIAL FLAME TOWARD SAID OPEN CHAMBER END; MEANS FOR FORCING AIR THROUGH SAID INLET INTO THE CONFRONTING PART OF SAID CHAMBER TRANSVERSELY THEREOF; AND A TUBULAR CERAMIC LINER IN SAID CHAMBER BETWEEN SAID OPEN END THEREOF AND SAID BURNER END AND PROVIDING A THROUGH-PASSAGE SUBSTANTIALLY COAXIAL WITH SAID CHAMBER, SAID CHAMBER BEING OF A CROSS-SECTIONAL DIMENSION SEVERAL TIMES LARGER THAN SAID DIMENSION D AND BEING BETWEEN SAID CLOSED CHAMBER END AND LINER OF A LENGTH SEVERAL TIMES LARGER THAN SAID CROSS-SECTIONAL CHAMBER DIMENSION, SAID BURNER END BEING LOCATED BETWEEN SAID AIR INLET AND LINER AND AXIALLY SPACED FROM SAID LINER A DISTANCE SEVERAL TIMES LARGER THAN SAID DIMENSION D, AND SAID AIR INLET BEING OF A MEAN CROSS-SECTIONAL DIMENSION SEVERAL TIMES LARGER THAN SAID DIMENSION D TO COMPEL THE FORCED AIR TO SET UP AIR TURBULENCE IN SAID CONFRONTING CHAMBER PART CROSSSECTIONALLY THROUGHOUT, WITH SAID AIR INLET BEING SO SPACED FROM SAID CLOSED CHAMBER END THAT THE END PART OF SAID CHAMBER THEREBETWEEN IS ONLY SEVERAL TIMES SHORTER THAN THE LENGTH OF SAID CHAMBER BETWEEN SAID CLOSED END THEREOF AND SAID LINER, WHEREBY SAID CHAMBER END PART WILL SERVE AS AN AIR DOME IN LARGELY SUPPRESSING AIR TURBULENCE IN SAID CHAMBER AND COMPELLING SUBSTANTIALLY UNIFORM AND NON-TURBULENT AIR FLOW PAST A FLAME FROM SAID BURNER END AND INTO SAID LINER PASSAGE. 